Fluorescence correlation spectroscopy (FCS) is a method wherein the fluorescence fluctuations (variations of the fluorescence intensity in time) of fluorescent molecules in a measured sample are measured and autocorrelation functions are determined from the fluorescence fluctuations to analyze the translational diffusion motions, etc., of the fluorescent molecules. By FCS, for example, the binding and motion of a single protein molecule can be analyzed.
Examples of conventional analyzers that make use of FCS include those described in Document 1 (Japanese Patent Application Laid-Open No. 2000-166598), Document 2 (Japanese Patent Application Laid-Open No. 2001-272346), and Document 3 (Japanese Patent Application Laid-Open No. 2001-194305). With the analyzer described in Document 1, a point-like excitation light is illuminated onto a single point of a measured sample and the fluorescence emitted from the measured sample is detected by a detector, such as a photomultiplier tube (PMT) or an avalanche photodiode (APD). With the analyzer described in Document 2, pulse excitation light is illuminated onto a measured sample while scanning and the fluorescence from the measured sample is detected by a CCD camera.